The use of steering knuckles for carrying wheel assemblies is a long established practice for providing steerability to vehicle axles. As such, in addition to their use on various automobiles, steering knuckles are employed on a large number of commercial, light and heavy duty trucks in use today, and are utilized with both permanent (fixed) and auxiliary lift-type axles.
Steering knuckles of the known-type are generally constructed of upper and lower yoke arms carrying rigidly mounted upper and lower bosses (each having an aperture for receipt of a kingpin), as well as having a main body comprised of an integrated or press fit spindle extending centrally therefrom (for mounting a wheel assembly thereon). In conventional steerable axle construction, the beam of the axle normally includes a kingpin mounted at each end in a generally vertical orientation for assembly of a steering knuckle thereto. When assembled, the steering knuckle is mounted so that the kingpin ends reside i.e. ride in the apertures of the upper and lower bosses so that the knuckle can rotate back and forth about the axis of the kingpin thus providing steerability. Although conventional steering knuckle designs are widely used in the automotive arts, various drawbacks concerning the difficulties in assembly of such designs, as well as their wear rates during operation, have been discovered.
More particularly, because a kingpin is typically press-fit into an axle and thus referred to as “fixed” in location prior to assembly of a steering knuckle thereon, and because, in conventional steering knuckle design, a knuckle is of one-piece construction, there is substantial labor required to assemble such a steering knuckle to a “kingpinned” axle. Furthermore, maintenance or repair of a steering knuckle assembly is difficult because of the complications inherent in removing a one-piece steering knuckle from a fixed kingpin. Moreover, because of differences in manufacturing tolerances as well as differences in axle and kingpin designs (which may come from different manufacturers), the “fit” of a steering knuckle on a individual axle may often be imperfect and adjustments often must be made to improve the fit in order to achieve optimum performance and/or wear characteristics.
For example, after assembly of a steering knuckle to a kingpin, if there is a space between the kingpin seating area (the area of the axle surrounding the kingpin) and the upper or lower boss (thus leaving a gap between the axle and the boss such as gap “G” in FIG. 4b), unwanted movement of the kingpin relative to the knuckle occurs during vehicle operation. More specifically, when such a gap between a boss and the axle exists after assembly, the kingpin is prone to oscillate within the apertures of the bosses when a vehicle employing the axle is operated. This oscillation (i.e. pumping of the kingpin in and out of the boss apertures), in turn, creates alternating high and low pressure pockets within the boss apertures that create a vacuum which sucks up dirt or other debris into the bosses, ultimately causing wear to the kingpin as well as to the bearing and/or bushing surfaces located within the apertures of the bosses.
Several prior art attempts have been made to solve these problems associated with the failure to acceptably seat the steering knuckles and contacting parts in steerable axles, particularly in heavy duty vehicles such as trucks and trailers.
One known prior art technique for solving this problem involves manually adding shims over the kingpin during knuckle installation to occupy unwanted space between the bosses and the kingpin seating area. As will be recognized, this option requires additional labor and parts, and further relies on a trial and error approach when attempting to, hopefully, end up with the appropriate/ideal distance between bosses and the axle (i.e. the assembler must guess at the correct number of shims which must be added to eliminate the “gap”).
More recent attempts to solve this and other problems have involved the use of multi-piece knuckles employing bolt-on yokes or bosses such as exemplified by U.S. Pat. No. 6,367,825 (hereinafter the '825 patent). Although the '825 patent addresses the problem described herein, the range of adjustability which is achieved by the mechanism described in the '825 patent is finite (i.e. restricted) because adjustment is limited to the increments determined by the size of the teeth of the boss and knuckle (flange) mating portions i.e. the boss can only be adjusted a distance which is a factor of the size of the mating teeth.
It is, of course, desirable to have the capability to adjust the position of a boss in a greater number (e.g. non-finite number) of increments so as to create a more precise “fit”. In short, such adjustability would provide the capability for fine tuning the fit of a steering knuckle on a steerable axle thus reducing part wear rates and decreasing labor costs.
In view of the above, it is apparent that there exists a need in the art for apparatus which overcomes the above drawbacks. It is a purpose of this invention to fulfill this need, as well as other needs in the art which will become apparent to the skilled artisan once given the above disclosure.